The present invention relates to a multi-channel magnetoresistive head device using a lot of magnetoresistive heads which read information from a magnetic recording medium by using magnetoresistive films.
The magnetoresistive heads (hereinafter called as MR heads) utilizing magnetoresistance effect have been widely used in order to reproduce information recorded on magnetic recording medium such as hard discs, video tapes etc. In recent years, the tendency to the multi-channels of the MR heads have been grown due to the development of the micro-fabrication technique of semiconductors.
FIG. 4 is a diagram showing a multi-channel magnetoresistive head device 11. As shown in FIG. 4, the multi-channel MR head device 11 includes a wafer substrate 12, a plurality of MR heads 13 (13-1, 13-2, 13-3, . . .) formed on the wafer substrate 12, and a plurality of electrode pads 14, 16 electrically coupled to MR elements and coils constituting the MR heads 13, respectively. The electrode pads 14, 16 are electrically coupled to a plurality of electrode pads 17, 19 provided on a flexible printed board 40 through wires 15, 18, respectively.
In this multi-channel MR head device 11, the MR heads 13 are disposed so as to oppose to a magnetic recording medium such as a hard disc, a video tape etc. on which predetermined information is magnetically recorded, whereby the information recorded on the recording medium is read by utilizing the change of the resistance values of the MR elements while supplying a predetermined current to the MR elements constituting the MR heads 13. The signals read from the MR elements are supplied through the flexible printed board 40 to a predetermined circuit within the main body of a recording/reproducing apparatus such as a hard disc drive, a video tape recorder etc. in which the multi-channel MR head device 11 is provided.
In the multi-channel MR head device 11 shown in FIG. 4, in order to supply the current to the respective MR elements constituting the MR heads 13 and supply signals read from the respective MR elements to the circuit within the main body of the recording/reproducing apparatus, two electrode pads 14 are provided in correspondence to each of the MR elements and two electrode pads 16 are provided in correspondence to each of coils used for recording on the recording medium. In such a multi-channel MR head device 11, when the number of channels is increased, that is, when the number of the MR heads 13 is increased, it is required to increase the number of the electrode pads 14, 16 as four times as the increase of the number of the MR heads. In this case, since the width of the substrate 12 is restricted, it is required to form the electrode pads 14, 16 so as to reduce the areas thereof.
The electrode pads 14 and the electrode pads 16 are usually coupled to the wires 15 and the wires 18 through use of the wire bonding, respectively. However, when the area of each of the electrode pads 14, 16 becomes narrower, it becomes difficult to perform such wire bonding procedure and so the efficiency of the procedure degrades.
On the other hand, when the area of each of the electrode pads 14, 16 is secured to a certain value, the number of the electrode pads 14, 16 which can be formed on the substrate of the same size is reduced. Thus, the number of the MR heads 13 which can be formed on the substrate reduces and so a desired number of the channels can not be obtained. Further, when the size of the substrate is made larger, the size of the multi-channel MR head device 11 itself becomes larger, so that it is not desirable for the apparatus which is required to be miniaturized.
The invention has been made in view of the aforesaid problems, and an object of the invention is to provide a magnetic head device which can increase the number of electrode pads formed on a substrate with a predetermined size without reducing the size of each of the electrode pads.
In order to achieve the above object, according to the present invention, there is provided a multi-channel magnetoresistive head device, comprising:
a wafer substrate;
a plurality of magnetoresistive heads arranged on the wafer substrate;
a plurality of electrode pads arranged on the wafer substrate in a first direction, and each electrically connected to an associated magnetoresistive head;
wherein respective adjacent electrode pads are shifted from each other in a second direction perpendicular to the first direction.
Preferably, the shifted amount of the adjacent pads in the second direction is larger than a dimension of the electrode pad in the second direction.
Preferably, the head device further comprises a flexible printed board, on which a plurality of electrode pads are arranged in a third direction. Each of the electrode pads on the flexible printed board is electrically connected to an associated electrode pad on the wafer substrate. Respective adjacent electrode pads are shifted from each other in a fourth direction perpendicular to the third direction.
Preferably, the shifted amount of the adjacent pads in the fourth direction is larger than a dimension of the electrode pad in the fourth direction.
In the above configurations, much more electrode pads can be formed on a substrate having a predetermined area, without reducing the area of each of the electrode pads. Therefore, the invention can cope with the increase of the channels of the multi-channel magnetoresistive head device. Further, since it is not necessary to reduce the area of each of the electrode pads, the working efficiency of the wire bonding etc. can be well maintained.